Field of the Invention
The present invention relates to a transmission unit of a motor vehicle, with a transmission and with an electric motor coupled thereto in the axial direction. The invention also concerns such an electric motor.
Description of the Background Art
In at least partly automatic transmissions of motor vehicles, the individual shift stages (gears) are set by means of a transmission actuator. For this purpose, the transmission actuator has a so-called selector finger and an electric motor, wherein the selector finger can be moved by the electric motor, and wherein the position of the selector finger determines the desired transmission ratio.
A brushless electric motor whose stator is supplied with current by an electronics unit is usually used as the electric motor. The electronics unit comprises a number of semiconductor components that are connected in a bridge circuit. The bridge circuit is customarily a three-phase bridge circuit, and the stator has three field windings that are connected to one another either in a delta or star circuit. For shielding and to avoid any damage to the field windings, the stator is located in a motor housing.
It is known from WO 2010/108532 A2, which corresponds to US 20120031215, to attach the electronics unit to the stator housing by means of screws. The electronics unit in this design is thermally insulated from the stator housing in order to avoid an exchange of heat from the stator housing to the electronics unit and a cooling element located thereon. The electronics unit is thus in uninsulated contact with the stator and the stator housing only through the screws and the elements required for driving the field windings. The stator itself is located in a recess in a transmission housing and is screwed thereto.
A drive shaft of the electric motor is designed as a worm gear shaft and projects into the interior of the transmission housing. The drive shaft in this arrangement is supported by means of two bearings designed as ball bearings, which are axially offset relative to one another. Located between the two bearings is a radial shaft seal that seals the region of the recess and the region of the interior of the transmission.